Responses of earthworm communities to crop residue management after inoculation of the earthworm Lumbricus terrestris (Linnaeus, 1758)

Earthworms are important for soil functioning in arable cropping systems and earthworm species differ in their response to soil tillage and crop residue management. Lumbricus terrestris (Linnaeus, 1758) are rare in intensively tilled arable fields. In two parallel field trials with either non-inversion (NIT) or conventional tillage (CT), we investigated the feasibility of inoculating L. terrestris under different crop residue management (amounts and placement). Simultaneously, we monitored the response of the existing earthworm communities to L. terrestris inoculation and to crop residue treatments in terms of earthworm density, species diversity and composition, ecological groups and functional diversity. L. terrestris densities were not affected by residue management. We were not able to infer effects of the inoculation on the existing earthworm communities since L. terrestris also colonized non-inoculated plots. In NIT and two years after trial establishment, the overall native earthworm density was 1.4 and 1.6 times higher, and the epigeic density 2.5 times higher, in treatments with highest residue application (S100) compared to 25% (S25) or no (S0) crop residues, respectively. Residue management did not affect earthworm species composition, nor the functional trait diversity and composition, except for an increase of the community weighted means of bifide typhlosolis in S0 compared to S100. In CT, however, crop residues did have a strong effect on species composition, ecological groups and functional traits. Without crop residues (S0), epigeic density was respectively 20 and 30% lower than with crop residues placed on the soil surface (S100) or incorporated (I100). Community composition was clearly affected by crop residues. Trait diversity was 2.6 to 3 times larger when crop residues were provided, irrespective of placement. Crop residues in CT also resulted in heavier earthworms and in a shift in the community towards species with a thicker epidermis and cuticle, a feather typhlosolis shape, and a higher average cocoon production rate. We conclude that earthworm communities under conventional tillage respond more strongly to the amount of crop residue than to its placement. Under non-inversion tillage, crop residue amounts affected earthworm communities, but to a smaller degree than under conventional tillage

A community trait-based approach to ecosystem functioning in soil

Functional traits capture characteristics of organisms that determine their individual response to environmental pressures, providing a mechanistic understanding of habitat responses and the effects on ecological processes. Trait-based approaches have already been reported for separate soil groups like bacteria, nematodes and collembolans but investigating these groups together could bring better insights in assessing both environmental pressures and state of the systems. Still, selecting a suite of single traits that might encompass the large heterogeneity in soil biota remains a challenge for community trait-based analyses.We sampled arable fields and their adjacent (buffer zone) margins to investigate overall trait-based responses of the soil community to agricultural management. We explored the suitability of three groups of functional traits (i.e. eco-physiological traits, behavioural traits and faunal morphological traits) to analyse how different components of the soil biota (fungi, bacteria, micro- and mesofauna) respond to agricultural management and to what extent the selected traits detect effects on soil functioning. For microbes, we opted for eco-physiological trait proxies due to the difficulties to study these organisms at individual level. Our results showed that eco-physiological traits reflected differences in nutrient cycling dynamics and carbon storage driven by the soil microbial community. The structural organization of micro- and the mesofauna trophic grouping and body mass distribution reflected effects of agricultural management on soil assemblages and revealed differences in the responses of these groups to the environment. We recognize some methodological limitations of our comprehensive community trait-based approach. Yet our analysis reveals characteristics of the soil community structure and belowground ecological processes, as i.e. the partial shift from the bacterial- to the fungal-driven energy channels, that could not be detected by traditional methods, showing the potential of this approach in determining environmental pressures and in evaluating ecosystem services.<br/

Functional diversity in nematode communities across terrestrial ecosystems

Functional diversity can be defined as the distribution of trait values within a community. Hence, functional diversity can be an indicator of habitat filtering and a reliable environmental predictor of ecosystem functioning. However, there is a serious lack of studies that test how functional diversity indices change depending on the environmental conditions. The aim of this study is to provide such evidence by analyzing the distribution and variation of continuous body-mass values (i.e. functional diversity) and related shifts in body length and width in a nematode community. We used a large online dataset on nematode traits to analyze: (i) the distribution of body mass using three functional diversity indices, i.e. functional richness, functional divergence and functional evenness; (ii) the shifts in body-size traits (length and width); and (iii) the body-mass distributions of five trophic groups and of the entire nematode community. Managed grasslands exhibited the widest range of body-mass values while body-mass distribution in arable fields covered the greatest area in comparison to the other ecosystem types. The shift in body size revealed environmental filters that could not have been identified by the study of functional diversity indices per se. We found low values of functional evenness to be associated with high values of functional richness. We provide novel empirical evidence that body-mass distribution within a trophic group mirrors the effects of habitat filtering more than the distribution in the community as a whole. Hence, our trait-based approach, more than functional diversity itself, disclosed soil food-web structure and identified community responses.</p

The chemical convergence and decomposer control hypotheses explain solid cattle manure decomposition in production grasslands

Recently, we reported for the first time that home field advantage (HFA) of litter decomposition also exists in agricultural production systems, in addition to earlier reports from natural ecosystems. Here, we provide evidence that adaptation of the soil decomposer community to differences in the chemical composition of solid cattle manure (SCM) explains the HFA. Two dairy farms were selected which differed in type of home-produced SCM (high-quality stacked or low-quality composted SCM) and soil type (sand or peat). Manure was exchanged between these two farms. Also, manure was incubated in fields of two neighbouring non-SCM farms. Using litterbags with three different mesh-sizes (125 μm, 1.5 mm, and 4 mm), we investigated the contribution of microbiota, mesofauna and macrofauna, to SCM dry matter (DM) and nitrogen (N) disappearance after 60, 120 and 240 days of litterbag placement. Home field advantage was estimated after accounting for effects related to structural differences in manure quality (quality index) and grassland soil biota communities (ability index). We found HFA in meso- (14–34%) and macro-mesh (19–31%) size litterbags. In micro-mesh litterbags, the HFA for dry matter and nitrogen disappearance was significant only after 120 days (18 and 26%, respectively). With time, trends of initial increase and then decrease in HFA of both aforementioned parameters were observed, but these were not significant. The quality index indicated that the composted manure had a lower dry matter and nitrogen disappearance rate compared to the stacked manure, irrespective of the location of incubation. The difference between the two manure types for N disappearance had vanished at day 240. Also, the chemical composition of the manure that remained in the litterbags changed over time. After 120 days, the C:N ratio of SCM at home was significantly higher compared to the translocated SCM (

Functional diversity in nematode communities across terrestrial ecosystems

Functional diversity can be defined as the distribution of trait values within a community. Hence, functional diversity can be an indicator of habitat filtering and a reliable environmental predictor of ecosystem functioning. However, there is a serious lack of studies that test how functional diversity indices change depending on the environmental conditions. The aim of this study is to provide such evidence by analyzing the distribution and variation of continuous body-mass values (i.e. functional diversity) and related shifts in body length and width in a nematode community. We used a large online dataset on nematode traits to analyze: (i) the distribution of body mass using three functional diversity indices, i.e. functional richness, functional divergence and functional evenness; (ii) the shifts in body-size traits (length and width); and (iii) the body-mass distributions of five trophic groups and of the entire nematode community. Managed grasslands exhibited the widest range of body-mass values while body-mass distribution in arable fields covered the greatest area in comparison to the other ecosystem types. The shift in body size revealed environmental filters that could not have been identified by the study of functional diversity indices per se. We found low values of functional evenness to be associated with high values of functional richness. We provide novel empirical evidence that body-mass distribution within a trophic group mirrors the effects of habitat filtering more than the distribution in the community as a whole. Hence, our trait-based approach, more than functional diversity itself, disclosed soil food-web structure and identified community responses.</p

Microbial catabolic diversity in and beyond the rhizosphere of plant species and plant genotypes

Microorganisms in the rhizosphere drive important ecosystem processes such as nutrient cycling and organic matter decomposition. Microbial activity in the rhizosphere is a function of both rhizodeposition and the soil's inherent microbial community. In this study, we investigated plant species and genotype effects on microbial functioning in the rhizosphere and compared it to the corresponding bulk soil. We investigated the rhizospheres and bulk soils from eight natural grassland species (four grasses and four forbs) in a long-term biodiversity experiment and genotypes of two crop species (Solanum tuberosum and Brassica juncea) in a short term experiment. Soil microbial functioning was assessed by determining microbial catabolic diversity, which is the microbial response to addition of several carbon-rich substrates. Substrate-induced respiration was higher in the rhizosphere than in the bulk soil for all plant species and genotypes, except for the grasses Agrostis capillaris, Anthoxanthum odoratum and Holcus lanatus, which yielded similar microbial activities in the two soil zones. Microbial catabolic profiles in the rhizospheres of Rumex acetosa, Leucanthemum vulgare and Plantago lanceolata were most distinct from each other and from the other grassland species. The bulk soil's microbial community catabolic profile was also species dependent. For S. tuberosum we found a genotype effect on the microbial catabolic profile in the rhizsophere but not in the bulk soil. For Brassica juncea no such genotype effects were found in the rhizosphere or bulk soil. This is a first step to link microbial rhizosphere activities to soil functioning in natural and agricultural ecosystems.</p

Информационно-аналитические программы на государственных телевизионных каналах

Assessing soil microbial functionality has the potential to reveal meaningful effects of soil management on soil processes influencing soil quality. We used MicroResp™ to assess microbial respiration upon the addition of six carbon substrates (glucose, alanine, aminobutyric acid, N-acetyl glucosamine, alpha-ketoglutaric acid, and lignin). From this, we calculated the multiple substrate induced respiration (MSIR), the microbial catabolic profile expressed as absolute and relative utilization rate, and the Shannon microbial functional diversity index (H′). We tested the effect of tillage (reduced vs. conventional) and organic matter addition (high vs. low) on these microbial parameters in soil from 10 European long-term field experiments (LTEs), and investigated their relationships with labile organic carbon fractions and various soil parameters linked to soil functions. Reduced tillage and high organic matter input increased MSIR compared to conventional tillage and low organic matter input. In addition, reduced tillage resulted in a small but significant increase in functional diversity compared to conventional tillage. An increase in soil management intensity (CT-Low > CT-High > RT-Low > RT-High) was associated with lower utilization of all the substrates expressed as absolute utilization rate, and a proportionately higher utilization of alpha-ketoglutaric acid compared to the other substrates. More intensive management systems also showed lower soil quality as measured by various soil parameters, in particular total and labile organic carbon, basal respiration, and microbial biomass nitrogen. The present work shows for the first time the key role of labile organic carbon, as affected by soil management, in determining microbial functional diversity. Aggregating results from 10 European arable LTEs, making use of a comprehensive dataset, MicroResp™ showed that reduced tillage and increased organic matter addition created a more favourable habitat for the microbial community to utilize different carbon substrates and, thereby, the potential for nutrient cycling.</p

Microbial catabolic diversity in and beyond the rhizosphere of plant species and plant genotypes

Microorganisms in the rhizosphere drive important ecosystem processes such as nutrient cycling and organic matter decomposition. Microbial activity in the rhizosphere is a function of both rhizodeposition and the soil's inherent microbial community. In this study, we investigated plant species and genotype effects on microbial functioning in the rhizosphere and compared it to the corresponding bulk soil. We investigated the rhizospheres and bulk soils from eight natural grassland species (four grasses and four forbs) in a long-term biodiversity experiment and genotypes of two crop species (Solanum tuberosum and Brassica juncea) in a short term experiment. Soil microbial functioning was assessed by determining microbial catabolic diversity, which is the microbial response to addition of several carbon-rich substrates. Substrate-induced respiration was higher in the rhizosphere than in the bulk soil for all plant species and genotypes, except for the grasses Agrostis capillaris, Anthoxanthum odoratum and Holcus lanatus, which yielded similar microbial activities in the two soil zones. Microbial catabolic profiles in the rhizospheres of Rumex acetosa, Leucanthemum vulgare and Plantago lanceolata were most distinct from each other and from the other grassland species. The bulk soil's microbial community catabolic profile was also species dependent. For S. tuberosum we found a genotype effect on the microbial catabolic profile in the rhizsophere but not in the bulk soil. For Brassica juncea no such genotype effects were found in the rhizosphere or bulk soil. This is a first step to link microbial rhizosphere activities to soil functioning in natural and agricultural ecosystems.</p

Earthworm communities in arable fields and restored field margins, as related to management practices and surrounding landscape diversity

Agricultural intensification has negative impacts on biodiversity at spatial scales from field to landscape. Earthworms are important for soil functioning, so it is crucial to understand the responses of earthworm communities to agricultural management and land use. We aimed to: 1) investigate whether earthworm communities differed between relatively undisturbed field margins, and highly disturbed arable fields; and 2) quantify how earthworm communities of arable fields and field margins are affected by three environmental filters, i.e. soil properties, management practices, and composition of the surrounding landscape. Earthworms were sampled in 26 arable fields and 15 field margins, across a polder area in The Netherlands. While earthworm density, total biomass and species richness did not differ significantly among arable fields and field margins, rarefied earthworm species richness and community composition did. The three environmental filters affected earthworm communities of arable fields and field margins differently. In arable fields, earthworm communities were explained by arable management only (26%). In contrast, all three filters contributed significantly to the variation in earthworm communities of field margins, where management practices explained a larger part of the variation (18%) than the surrounding landscape (11%) and soil properties (10%). Our results suggest that soil properties and surrounding landscape can affect earthworm communities of field margins. However, in the arable fields, where more diverse lumbricid communities are desirable to improve soil functions, such influences are negated by the impact of management at field scale. We demonstrated that field margins enhance earthworm biodiversity in arable landscapes, but surrounding landscape and field margins had limited impact on earthworm communities in arable fields. Decision-making and research should focus on less intensive management options for arable fields to stimulate earthworms and earthworm-mediated soil functions